1. Field of the Invention
This invention relates to a wireless communication device, a wireless transmission system and a wireless communication method.
2. Description of the Related Art
As a technique for implementing a high-speed signal transmission between different electronic apparatus disposed in a comparatively short range (for example, within several centimeters to ten and several centimeters), or within an electronic apparatus, for example, a LVDS (Low Voltage Differential Signaling) is known. However, together with further increase of the amount of transmission information and further increase of the speed of transmission recently, increase of power consumption, increase of an influence of signal distortion by reflection and so forth, increase of unnecessary radiation and so forth have become problems. For example, the LVDS reaches a limit where a signal such as a video signal (including an image pickup signal), a computer image or the like is transmitted at a high speed (on the real time basis) in an apparatus.
As a countermeasure against the problem of increase of the speed of transmission data, it seems a possible idea to increase the number of wiring lines to decrease the transmission speed per one signal line by parallel transmission of signals. However, the countermeasure just described gives rise to increase of the number of input and output terminals. As a result, complication of a printed board or a cable wiring scheme, increase of the size of a semiconductor chip and so forth are required. Further, since a large amount of data is transmitted at a high speed along a wiring system, a problem of electromagnetic field interference occurs.
All of the problems involved in the LVDS or the technique of increasing the number of wiring lines are caused by transmission of a signal through an electric wiring line. Therefore, as a method for solving a problem caused by transmission of a signal along an electric wiring line, methods in which electric wiring lines for signal transmission are eliminated have been proposed (see, for example, Japanese Patent Laid-open Nos. 2005-204221, 2005-223411, Hei 10-256478 and U.S. Pat. No. 5,754,948, hereinafter referred to as Patent Documents 1 to 4, respectively).
Patent Documents 1 and 2 propose carrying out signal transmission within a housing by wireless and applying the UWB (Ultra Wide Band) communication method. Patent Documents 3 and 4 disclose use of a carrier frequency in the millimeter waveband.